SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ab91f428ad9f3d401627d5f732fb9e73f5bbfd2db28d09c2f6a7f2e9fe6c146' 
  AND token = 'LEcZxo3AnuQAoiNWE8pJHVmHYPVD8RSh+STHGTPoqt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}